1. Field of the Invention
The present invention relates to a light emitting element, and more particularly, to a light emitting element including a wavelength-converting layer arranged on an upper surface of a light emitting diode (LED) chip. The wavelength-converting layer may reduce a color variation generated between a vertical surface and a side of the LED chip.
2. Discussion of the Background
Methods for realizing a white light source using LEDs may be classified into: a method for combining an LED chip emitting blue light and a yellow phosphor; a method for combining an LED chip emitting blue light, an LED chip emitting red light and an LED chip emitting green light without any combination of phosphors; and a method for combining an ultraviolet (UV) LED chip emitting ultraviolet rays and red, green and blue phosphors. Among these methods, the combination of an LED chip emitting blue light and a yellow phosphor has been generally widely used.
When combining an LED chip emitting blue light with a yellow phosphor, the yellow phosphor may be dotted onto the LED chip in a dispensing or piezo manner, or a conformal coating method may also be used. The conformal coating method may adopt electrophoresis, spraying, attachment of a wavelength-converting sheet, or the like.
Among the conformal coating methods, the method of attaching a wavelength-converting sheet may allow uniform emission of light with a desired wavelength when the wavelength-converting sheet has the same area as the upper surface of the LED chip. However, if the area of the wavelength-converting sheet is smaller or greater than the area of the upper surface of the LED chip, certain problems may occur. In a case where the area of the surface of the wavelength-converting sheet contacting the upper surface of the LED chip is smaller than the area of the upper surface of the LED chip, the light output from the LED chip may be partially emitted without wavelength conversion, which results in irregular distribution of white light and occurrence of a blue ring. On the other hand, in a case where the area of the surface of the wavelength-converting sheet contacting the upper surface of the LED chip is greater than the area of the upper surface of the LED chip, the wavelength-converting sheet may move in a predetermined direction due to fluidity of an adhesive material for attaching the wavelength-converting sheet to the LED chip, so that the light output from the LED chip may be partially emitted without wavelength conversion.